As microwave energy becomes increasingly present in our environment, an unmonitored population is placed at risk while we must admit to data regarding the biologic effect of such exposure. The basic aim of this project will be to determine the effects of a long term (4 months) exposure to microwave radiation (MWR) at low incident power densities. Our intent will be to examine behavioral, adrenocortical, and serotonin related effects of administratively safe MWR (i.e., less than 10 mW/cm squared incident power density). Data will be obtained from several behavioral and biochemical variables, and we will define a dose-response curve over the range 0-20 mW/cm squared. The chronic MWR environment will comprise a pair of RF anechoic chambers into which control and experimental groups will be introduced for eight hours of whole body MWR exposure per day. Pulse modulated MWR at 2450 MHz will be used. In the first part of this study, the effects of 0, 10, and 20 mW/cm squared MWR on open field behavior and on instrumental behavior for liquid reward will be determined in rats. Besides the 0 mW/cm squared group, an additional control group will be exposed to a mild thermal stress. In the second part of this study and to initiate the extrapolation of the results to human exposure, the instrumental behavior of monkeys for liquid reward during chronic MWR will be determined. Again, dose-response curve will be defined, via radiation at 5, 10, and 20 mW/cm squared with dual control groups, are above. Coincident with these behavioral studies, 24 hour urine samples of selected subgroups of rats and monkeys will be quantitatively analyzed for stress-related steroid fractions and for excreted 5-hydroxyindoleacetic acid. These studies will provide new and needed data regarding the extent to which low level MWR specific effects can be understood as secondary to mild thermal stress. A pattern of MWR specific responses that departs from that induced by ambient thermal stress, under identical conditions, would suggest that the results of chronic MWR encompass more than a hypothalamic reaction to thermogenesis. Null or negative results would enable us to more critically evaluate the extent of the risk derived from chronic, whole body MWR exposure of the adult animal.